Which two molecules bond together to form a disaccharide?

A. Carbon dioxide and water

B. Two water molecules

C. Fructose and glucose

D. Nucleic acid and protein

The answer is C. Fructose and glucose.

A disaccharide is a carbohydrate composed of two (prefix di-) monosaccharides bound by glycosidic bonds. The only monosaccharides among all choices are fructose and glucose. They together form disaccharide sucrose.

Other choices could not be correct because all mentioned molecules are not carbohydrates at all.